Ancient altercations between musk turtles and alligator gar recorded in Florida's fossil record
- Paleontologist Jason Bourque recently described a new, extinct species of musk turtle that lived in Florida during the late Miocene roughly five-and-a-half million years ago.
- The name given to the new species, Sternotherus pugnatus, is a nod to the turtle’s pugnacious behavior, as inferred from the many healed scratches, bite marks and broken bones it sustained during encounters with predators.
- One of the predators has been tentatively identified as an alligator gar or close relative based on small tooth fragments embedded in the turtle shells.
- The fossils were found in what’s referred to as the “turtle death layer” at the Montbrook fossil site, which contains hundreds of shells. This layer may have formed when turtles congregated in a shrinking pool of water during a drought. Though shells are abundant, associated skulls and limbs are inexplicably absent.
Sometime between 5.5 and 5.6 million years ago, two shell crushers squared off in the languid currents of an ancient Florida river. The fossils they left behind, discovered by paleontologists at the Florida Museum of Natural History, reveal the identity of the combatants and the outcome of their encounter.
In one corner, weighing in up to 370 pounds and growing up to 10 feet long, was one of North America’s largest freshwater fish, the alligator gar. The common name partially comes from their long snouts, which superficially resemble those of alligators but most obviously differ by having several additional rows of teeth. Their skulls are wrapped in thick cantilevered muscles that can pull the jaw down to full gape in close to a tenth of a second. This rapid movement, usually made in anticipation of a meal, creates a substantial amount of negative pressure that pulls the surrounding water — and anything suspended in it — toward the gar’s gullet and down into the lightless lower reaches of its alimentary canal.
On the opposing end was a humble musk turtle. These animals are small, even by turtle standards, and furtive, preferring to spend most of their time trawling muddy river bottoms and only rarely leaving the water to bask on logs and tree limbs, which they abandon at the slightest sign of danger. But “when [their] slow anger is aroused,” musk turtles can become a formidable adversary. Many of them have heads that are proportionally larger than other turtles and a correspondingly strong bite force that they use to crush snail and clam shells.
If threatened, they may resort to vigorously biting anything within their reach, which — given that some have necks they can twist at a 180-degree angle and extend all the way to their hind feet — is considerably large. If that doesn’t work, musk turtles will often emit small drops of volatile acid from glands beneath their arms and legs. The resulting smell has been variously described as reminiscent of burning tires, cheesy garbage, bitumen and body odor.